In recent years, with the spread of compact terminals and the improvement of their performances, dedicated terminals for electronic books and contents distribution services, which were conventionally unrealistic, have been spread. In addition, with the electronic processing of books, terminals also have been provided that include not only text browsing functions but also reading functions with voice synthesis. Furthermore, with the spread of various electronic book formats (e.g., a digital accessible information system (DAISY)) taking into consideration persons with visual disabilities and persons with learning disabilities, contents in which reading voice data is embedded have been gradually spread, for example.
In general, electronic books essentially composed of texts are flow style data without having fixed pages. To point a certain position in an electronic book, designation based on text data is required. For copyright protection and security reasons, it is, however, often difficult or not permitted to directly access the text data.